BOBBI KRISTINA IS THAT AN ENGAGEMENT RING ON YOUR FINGER?

Whitney Houston's daughter was sporting an interesting piece of jewelry on her ring finger during her PDA-filled stroll with her "adopted" brother this week ... a big, fat ring.

As we previously reported, Bobbi Kristina and Nick Gordon finally went public with their relationship this week ... holding hands and kissing during a lunch date in Atlanta.

Now, with rumors swirling about a possible engagement ... the massive ring on Bobbi's finger isn't doing anything to hint otherwise.

Congrats ... maybe?